Percussive pneumatic tool



2 192 July 7 e. ELSTER PERCUSSIVE PNEUMATIC TOOL Filed Aug. 28. 1926 In ventor:

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UNITED STATES GUIDO ELSTER, OF HER-NE, GERMANY.

PERCUSSIVE PNEUMATIC TOOL.

Application filed August 28,1926. Serial NO. 132,233.

The known percussive pneumatic tools controlled by ball-valves, conical valves, cylindrical valves, flap-valves or other valves of similar simple construction permit a great percentage of live motive fluid to escape during .the time the valve changes its seats unused through the exhaust port or ports uncovered by the percussion bar or piston.

To avoid this serious drawback my present invention provides an axially movable valve-seat arranged on a stepped tubular slide adapted to interrupt the inflow of motive fluid into the operating cylinderchamber before the exhaust thereof has set in, i. e. before the valve has changed its seats. In doing so considerable volumes of live motive fluid are saved and a quiet run of the percussive pneumatic tool is assured.

In the accompanying drawing my invention is shown as applied to a pneumatic pick-hammer. in which drawing:

Figure 1 is a longitudinal sectional view. of said pneumatic tool wherein the axially movable valve-seat admits the motive fluid to the rear cylinder-chamber.

Figure 2 is a view similar to Figure 1 and shows the valve in a position wherein it excludes the motive fluid from both cylinder-chambers simultaneously.

Figure 3 is a partial longitudinal sectional view of the pneumatic tool wherein the valve and the axially movable valve-seat are in a position to permit the motive fluid to flow into the forward cylinder-chamber.

Figure 4 is an elevation of the pneumatic tool on a smaller scale.

of the valve structure on an enlarged scale.

The bore 1 of the cylinder 2 of the percussive pneumatic tool shown is at its lower end recessed and at its top closed by an 111-- termediate plate 3 upon which a valve-casing el is arranged and provided with a handle 5 preferably formed the valve-casing t are rigidly held together bybolts'6 and kept in alignment one with another by means of annular projections 7 and 8 of said intermediate plate. Of these project-ions the former is inserted into the cylindrical bore 1 and the latter into a recess 9 of the valve-casing t as indicated in Figures 1, 2 and 3. In the valve-casing at is arranged a thimble-shaped valve-cage :by a screw-plug 33. conical valve extends upward through the Figure 5 is a longitudinal cross-section integrally therewith The cylinder 2, the intermediate plate 3 and 10 provided with a head 11 preferably utilized as a stationary valve-seat 12 for a reciprocating ball-valve 18. The other seat ll of this valve is made axially movable and for this reason arranged at the upper end of a tubular slide 14:, which seat and slide will hereinafter be jointly designated as the sliding valve-seat 14. This valveseat is partly guided in said projection 7 and partly in a valve-cage and besides this it is provided with an annular pressureflange or step 15 adapted to move longitudinally in an annular recess 16 formed within said annular projection 8. The 1011- gitudinal movement of the sliding valveseat is bound on the one hand by the under "face of the-valve-cage 10 and on the other hand by-an annular 11m 17 arranged within said recess 16. This rim encircles a shallow annular excavation 155 connect-ed by a radial duct 19 to an auxiliary channel 20 arranged in a thickened portion of the wall of the cylinder 2 and connected by means of the two radial ports 21 and 22 with the bore 1 of the cylinder 2. e

The stationary valve-seat 12 opens into an inlet-channel 23 connected withthe forward cylinder-chamber 24 whilst the radial admission ports 25 of the valve-cagelO oaen into an annular chamber 26 connected by achannel 27 to a chamber 28 adapted to means of a conical valve 30 steadily urged toward its seat 31 by a spring-32 supported The spindle 34 of said handle 5 and may be pushed inward against the spring 32 by a lever 35 of U-shaped crosssection and hinged to said handle by a pin 36. see Figures 1,2and t.

To make the percussion-piston 37 strike against the tool 38- arranged in the usual manner in-the'front end of'the cylinder 2 and retained in place by a coiled tool-cage titl -the motive fluid (generally compressed air) is passed over the valve 30 previously unseated by means of the lever 85 and flows through the channel 27 into the chamber 26 lteeps the valve-seat 12 closed. Under .the pressure of-the motive fluid onthe rear face be connected at will'wit-h the inlet 29 by 37 of the percussion piston the latter is driven toward the tool 38 and thereby successively closes the radial port 21, the exhaust ports 41 and 42 and finally the radial port 22. At the moment the rear face 37' of the percussion piston uncovers said radial port 21 a part of the charge of the rear cylinder-chamber passes from the latter into the auxiliary channel 20, enters into the xcavation 18 and exerts within a recess 18 a pressure upon the under face of the annular pressure-flange of the sliding valveseat with the result that the latter is raised until pressed against the ball-valve 13, see Figure 2. To warrant a faultless action of the sliding valve-seat 14 ventholes 16 always in communication with the atmosphere are provided. During this elevated position of the sliding valve-seat the admission of motive fluid to the active cylinder-chamber 40 is interrupted, for which reason the motive fluid contained therein commences and continues to expand until the rear face 37 of the percussion piston opens the exhaust ports 41. At this moment the under face of the flange 15 of the sliding valve-seat is released from pressure so that the pressure of the motive fluid still exerted on the smaller annular topface 43 of the sliding valve-seat can return the latter into its bottom position. Simultaneously herewith theball-valve 13 drops on its seat 14 since the rear cylinder-chamber 4O communicates with the atmosphere and the upper half of the ball-valve is exposed to the pressure of the motive fluid. The sliding valve-seat 14 and the ball-valve 13 now occupy the position shown in Figure 3. In this position the stationary valve-seat 12 and the inlet-channel 23, connected with the forward cylinder-chamber 24, are opened for the admission of the motive fluid into said forward cylinder-chamber wherein it acts upon the frontal. face of the percussion piston and drives the latter toward the sliding valve-seat. During this motion the rear face of said piston first closes the exhaustports 42 and 41 and then the port 21 of the auxiliary channel 20 after which the front edge 44 of the percussion piston uncovers the port 22. At this moment a part of the charge contained in the'active forward cylinder-chamber 24 passes through the port 22 into the auxiliary channel 20, advances to the under face of the flange 15 of the sliding valve-seat and raises the latter and the ballvalve 13 supported by it until said valve is pressed upon its seat 12, Figure 2, in which position the parts 14 and 13 are retained on account of the greater pressure exerted on the under-face of the flange 15 as compared with the pressure exerted from the opposite direction on the smaller annular top-face 43 of the sliding valve-seat 14. During the continuation of the return stroke of the piston 37 the exhaust-ports 42 will be uncovered by the front edge 44 of said piston, at which moment the pressure in the auxiliary channel 20 and simultaneously therewith the pressure exerted upon the under face of the flange 15 will drop to atmospheric pressure, so that the sliding valve-seat 14 will be moved toward the tool 38 on account of the pressure exerted on the annular top-face 43. tnince the pressure of the motive fluid continues to act upon the lower half of the ballvalve 13 it will remain upon its seat so that at this moment the ball-valve and the sliding valve-seat will again occupy their initial position shown in Figure 1. The cycle of operations of the ballvalve, the sliding valve-seat and the percussion piston is now completed and may be repeated at will. To make the blows cease the lever 35 is released whereupon the spring 32 returns the valve 30 to its seat and thus puts the tool out of action.

I claim 1. A percussive pneumatic tool comprising a working cylinder, a percussion piston, a rigid valve-seat, a sliding valve-seat, a valve arranged between said valve-seats, and means arranged on said sliding valve-seat and adapted to operate the latter by a part of the charge to interrupt the inflow of mo tive fluid into the active cylinder-chamber before said percussion piston has opened the exhaust thereof.

2. K percussive pneumatic tool comprising a working cylinder, a percussion piston reciprocating therein, a rigid valve-seat, a

sliding valve-seat, a valve arranged between said valve-seats, a valve-casing, an intermediate plate arranged between said cylinder and said valve-casing, a pressure-flange seated on said sliding valve-seat and adapted to move axially in a recess provided in said intermediate plate, an auxiliary channel arranged in the cylinder wall and communicating at the one end with the under face of said pressure-flange and at the otheiwend by a plurality of ports with the interior of said cylinder to lead a part of the charge of the active cylinder-chamber to the under face of said pressure flange to cause said sliding valve-seat to interrupt the inflow of motive fluid into said active cylinder-chamher before said percussion piston has opened the exhaust thereof.

3. A percussive pneumatic tool comprising a working cylinder, a percussion piston reciprocating therein, a valve-casing, an intermediate plate placed between said cylinder and said valve-casing, means on said. intermediate plate for keeping said cylinder and said valve-casing in alignment, a valve-cage, a stationary valve-seat arranged :in the head of said Valve-cage, a sliding valve-seat guided by said valve-cage and by said intermediate plate, an annular pressure-flange arranged on said sliding valve-seat and adapted to lOU move axially in a recess providedin said intermediate plate, a ball-valve arranged between said valve seats, an auxiliary channel seated in the cylinder-Wall and communicating at the one end with the recess provided in said intermediate cover plate and at the other end by two ports with the cylinderbore to be adapted to lead a part of the charge of the activev cylinder-chamber beneath the pressure-flange of said sliding 10 valve-seat to actuate the latter to interrupt the inflow of motive fluid into the active cylinder-chamber before said percussion piston has opened the exhaust ports thereof.

In testimony whereof I aflix my signature.

GUIDO ELSTER. 

